The overall purpose of this proposal is to examine the effects of early auditory input on the acquisition of normal speech and language, and how alterations in this input can contribute to language impairment. A child~s hearing status, auditory history (i.e., history of otitis media with effusion), ability of the child to process nonspeech auditory signals (i.e., simple and complex tones), ability to process speech signals without attached meaning, ability to process meaningful language, and exposure to a second language all can affect normal language development. To understand language and its disorders it is necessary to examine the levels of auditory processing (acoustic-phonetic-linguistic) in a systematic fashion. Four interrelated projects will examine these issues. Project 1 will investigate auditory processing at peripheral and central levels using behavioral, psychoacoustic, physiologic and electrophysiologic measures. Project 2 uses an event-related potential (ERP) mismatch negativity (MMN) to assess pre- attentive, automatic processing of acoustic events. Project 3 employs both behavioral and electrophysiological measures to determine whether the deficits seen in SLI are at the level of discrimination of acoustic-phonetic distinctions or at the level of categorization of these distinctions into language (i.e., phonemic categories). Project 4 extends the investigations from the acoustic/phonetic to the lexical (word) level processing using behavioral and electrophysiologic measures. Project 5 examines the effects of training or alteration of auditory input on spoken language. The study populations will be 1) children with specific language impairment; 2) children with history of otitis media with effusion that results in mild fluctuation hearing loss at a critical time in language acquisition; 3) children with congenital mild to moderate-severe cochlear (sensory hearing loss; 4) infants with "paradoxical" early auditory status findings (abnormal brainstem response in the presence of normal otoacoustic emissions); 5) bilingual children; and 6) normally developing children.